Delayed voltage responsive system utilizing capacitor controlled thyratrons



July 25, 1950 ROTA 2,516,348

R. M. SE DELAYED VOLTAGE RESPONSIVE SYSTEM UTILIZING CAPACITOR CONTROLLED THYRATRONS Filed June 20, 1945 mom/WM "UNITED "STATE l atente d July 25 1950 Rudolph M.-Serota, Milwaukee, Wis, assign'or to Allis-Chalmers -Manufacturing Company, -Milwaukee, Wisr, a corporation of Delaware S PATENT OFFICE Application June 20, 1945, SerialNo. 600,508

7 I 6Glaims. l

invention-relatesin general to improvements in f electric control systems and more particularly to voltage 'responsivecircuits for controlling theope'rationo'i translating devices such as voltageindicating means 'and'volta'gemegulating-means.

lhe Operation of tran'slatingdevices is often controlled by means of a :pair of relays which are selectivelyenergi'zed in response to variation of '2. Voltage or of another electrical quantity aboveand'below 'a' predeterminedrange of values. The relays may be energized througha pairof thy'ratrons of WhlCh'OIlE is responsive to variation of'the'quahtity abovea predetermined Value and the other is responsive to variation of the quantity below 'arrother predetermined value.

Thegrid circuits of'the'tw'othyratrons are then generally provide'd with separate adjusting means. *Such means ma serve for the coarse adjustment of'theoperating points'of the'thyratrons, and it is then advantageous to provide common fin'e adjustment means in the 'grid circuits of the thyratrons for simultaneously varying the voltages to which "the th'yfat'ron's are responsive without substantially changing their difierence. In regulating systems in which a'regulator is controlled by a'voltager'espons'ive system of the typeherein considered and in which the response of the"thyra'troiisis 'delayed'by'capacitors connected'to their grid circuits, it is advantageous to-dis'c'ohrict'atleast part of a'tim'e delay capacitor during operation or the associated thyratron to prevent 'oi 'eftrat'el of the regulator. The capacitdr iria'ythnbe given a charge for delaying subseqtem respdnse of the thyratron'beyond the timenorr'nall'y'required for such response to thereby prevent excessively frequent operation of the regulator. 'The delayeapacitor may also be used rorinipressmg a transient'potential on the thyratren'grio'u' on operation Of the thyratron to insure that the thyiatron -'Will continue to carry eur'rentrera substantial'length 'of t-ime.

It is therefore an object or the present invention 'to provide a voltage res onsive device cornprisi'ng common *mean's for simultaneously adjusting the r'espon'seor a pair'of'thy'ratrons to differentv'alue's or voltage.

Another object of the present invention is to provide a'n'electriocontrol system in which'time delay means 'controllingthe operandner a regulating device are rendered inoperative during eper non or the device.

Anothervobject of the present invention is to jilbv'ide an "electric contror system in which time '2 delay means controlling theoperation ofa regulating device are caused to impart an abnormally long delay to "anyresponse of the system immediately following completionofaan operation of the'device.

Another object of the' present invention is to provide a voltage re'spOnsive-syste'min whicha 'thyratronener'gized from-a source'of alternatin'g current'is so=controlled-as to carry current for vperiods always exceeding one cycle "of the voltage of thesource.

Objects and advantages other'than those above set-'iorth will be apparent from-the following description When read'in-connection with the accompanying drawing, which diagrammatically illustratesoneembodiment of the present-inven- 'tion applied to thebontrol of a feeder voltage regulator of thetapchanging type.

Referring'mo're particularly tothedrawing by characters'oi reference, numeral 6 designates an alternating current generator connected with a distribution'cir'cuit 'l' of which the voltage is to be regulated independentlybf the generator voltage. This'regulationis effected by-means oi" a regulator generally designated by B. The regulator may be of *any' suitable known typeand may comprise a transformer having a'primary winding '9 and secondary windings Hi,-l l. Winding 9 i'sconne'cted'across'circuitland is provided with a plurality of taps severally connected with the fixed contacts 12 of-a tap changer. The movable contacts H of the tap changer are connected with a'regulating winding l5 through a protecti've 'autot'ransiormer it. Winding 15 may be connected withone or the other conductor of cir- "cui-t 1 through a-selector switch I! to cause the regulator eithe'r to'buek or boostthe voltage of circuit '1. Winding '-'l5--is-inductively related with a Winding i8 serially connected with circuit 1 to "induce therein a voltage depending on the position of contacts Hand of switch it. Cont'acts lfl-may beactuated by-a reversible capacitor motor -20 through sui-table -known means (not shown) for insuring that the movable contacts always completeany'movement thereof initiated by the motor.

Theoper'ation of -reg-ulator8 is controlled by a voltage responsive system comprising a pair of current responsive relays l-9, 2-! for selectively connecting the stator windings of motor 20 with windingl l to causeregulator 8to raise or lower the voltageof "circuit '1. "Relays is, *21 may be energized from any "suitable source of electric current, and it is generally expedient to supply current to the relays from winding +0 through laying capacitor 59. Relay 2! is operable to disthe secondary winding 22 of a transformer having a primary winding 23 connected across winding 45. The connections of the coil 19a of relay l9 are completed through a current limiting resistor 2! and the plate circuit of a thyratron 25. Coil i911 is shunted by a current smoothing capacitor-29. Coil'2la of relay 2| is likewise connected with winding 22 through a current limiting resistor 3i and the plate circuit of a thyratron 32, and is bridged by a current smoothing capacitor 33. i

A variable voltage proportional to the voltage of a predetermined point of circuit 1 is impressed between a pair of conductors 34, 35 from wind? ings I0, 22 through circuit means comprising any suitable known line drop compensatorand an adjustable resistor 35. pensator may comprise, for example, a current The line drop com- I transformer 24 energized from circuit 4 and sup- 1 plying current to an adjustable resistor 25 and L an adjustablereactor 25. The operation of thyratrons 28, 32 is, controlled bymeans comprisinga pair of. voltage dividers connected in parallel across. conductors 34,, 35,. One of the voltage dividers comprises arectifying device such as adiode 31 having an, anode 31a connected with conductor 34 and a cathode 315 connected with conductor 35 .through a resistor 38 and a constant voltage device of any suitable known type such as a battery, a dynamoelectric machine or, preferably,.a dissymmetrical glow-discharge tube 39. Resistor 38 and tube 39 are bridged by a capacitor 4| for maintaining the potential of cathode 311) at a substantially constant value between successive cycles of the voltage of circuit 1. The othervoltage divider comprises a second diode 42 having. its cathode 42b connected with conductor. 34 and its anode 42a connected with conductor 35 through .a second resistor 43 and another constant voltage device such as a second glow discharge tube 44. Resistor 43 and tube44 are shunted by a capacitor 45similar to capacitor 4|.

The connections for energizing control grids 28c of thyratron 28 comprise. meansfor delaying the response of the thyratron to variations in the voltage of circuit 34, -35 including. suitable impedance means such as a resistor 45 connected between cathode 31b and cathode-44b of tube-4.4. An adjustable intermediate point of resistor, 45

is connected with grid 280 through a tap 4'! and through a resistor 48, and is connected with .conductor 35 through a relatively small delaying capacitor 49 as well as through contact Hat and a relatively large delaying capacitor'5i. Capacitor 5| may be disconnected from tap 4! by means of relay [9, which reconnects capacitor 5| through contact [9c and a resistor 53 with an adjustable tap of-a resistor 52 connected in parallel with tube 44. Contacts I9c, l9d are bridged byrelatively small capacitor 54. V

The connections for energizing control. grid "32c likewise comprise a resistor 55 connected between anode 42a of the diode 42 and anode 39a of tube 39. Resistor 55 is provided with an adjustare connected with an adjustable tap of a re sistor 62 connected across tube 44. Capacitors 63 to 66 are connected between the grids and the cathodes of the thyratrons to-prevent undesired operation of the thyratrons in response to transient voltages which may accidentally appear in grid circuits.

To insure uniform response of the system to the voltage of circuit 34, 35 the filaments of the diodes and of the thyratrons are energized from the latter circuitin any suitable known manner. Filaments 28c, 32e'may be connected with circuit 34, 35 through a suitable transformer 51. Filaments 31c, 420' may be likewise energized from a filament transformer or may be connected across circuit 34, 35 if they are designed for the voltage of the circuit. If diodes 3T, 42 are disposed in a common envelope they may be provided with a common filament likewise connected between conductors 34 and 35. I

It .will be apparent that each tapped resistor of thesystem may comprise an untapped portion connected .in series with a tapped portion to improve the accuracy of the adjustments that may be obtained therewith. One of the conductors of the system, conductor 35 for example, may-be grounded to the frame supporting the elements of the system either conductively or through a capacitor 68 forpreventing the appearance of disturbing alternating voltage components between the circuits of the system and the frame. v

The range of voltage response of the system and the time of response of the thyratrons may be varied in any desired manner by varying the elements of the system. It has been found that the. system operated satisfactorily to regulate the voltage of an actual distribution circuit by energizing circuit 34, 35 at 115 volts when the voltage of distribution circuit has the desired value and building the system ofelements identified by the following engineering data:

Thyratrons 28,32 Type 2050 Diodes 3.7; 42 Type 11'7Z6 Glow tubes 39, 44-; Type VR 105/30 Resistor 3B 200 ohms Resistors 21, 3! 2,500 ohms Resistor 43 5,000 ohms Resistor 38 7,500 ohms Resistor 53; 100,000 ohms Resistor 52' 550,000 ohms Resistors 4B, 55 'l megohm Resistor 62 1.5 megohm Resistors 48, 51 2 megohms Capacitors 63, 64,55, 66 0.002 microfarad Capacitor 69 0.1 microfarad j'Capacitors54, 6l 0.25 microfarad' Capacitors 49, 58; 1 microiarad Capacitors 4|, 45 2 microfarads Capacitors 54, BI 4 microfarads Capacitors 5|, 59 25 micro'farads The operation of the system will first be con-P able tap 55 connected with grid 32cthrougha resistor 51. Tap 55is connected with conductor 35 through a small delaying capacitor 58. and through contact Zld in series-with a large de- The screen grids 285, 32b.iof ,i

of circuit 1 corresponding to the adjustment of the line drop compensator is within the desired range of values for which the system is adjusted.

The voltage of winding l0 being proportional to thevoltage of generator 6 and the voltage of windinglz beingproportionalto the regulating voltage supplied-to circuit 1 from regulator 8, the voltage impressed on the plate circuits of the thyratrons is proportional to the regulated voltage at the terminals of regulator 3. Undersuch condition -the hyre ro ser .mei n l perative -by the potentials impressed on theficontrol grids thereof. Current is, however, supplied to the voltage dividers from windings 1-8, '22 through the line drop compensator, resistor 35 and'circuit 84,35. As the load-across-circuit 34, 35 is constant, the voltage thereof is also constant and has a predetermined value depending upon the adjustment'of resistor-36.

During the positive half-cycles of the voltage of circuit 1, diode 3! supplies charging current to capacitor "ii-l and also supplies'cu-rrent to resister tiland tube 39. During the negative half cycles, the flow or current throughtube 3 9'is' supplied from capacitor n l, which has --a sufiicient c-apacityto maintain the potential *of cathode 51b substantially constant from one 'cycle to=the*next. The potential or cathode -3lb however is "able to follow the-variations of the voltage of circuit 155 in response to variations -in the voltage of circuit 1 over periods including a relatlvely-large number ofcycles. Cathode 31b may thus be considered to constitute-a source of variable positive potential for-grid 28c. As-thevoltage-drop in tube remains substantially constant when 'the'current through the tube varies uvithin wide limits, anode iii-la may be considered to constitute a source-of constant positive potential iorgrid 32c.

Likewise anode 52d constitutes a source of variable negative potential for grid 32c and cathode i'db constitutes a source of constant negative potential for grid 28:2.

The potential of tap *4 and of grid 280 is intermediate the positive and negative potentials impressed on the terminals of resistor 455 irom the voltage dividers, and the potential of tap 56 and of grid 320 is intermediate the p'ositive and negative potentials impressed on the terminals of resistor 55iroro the voltage-dividers. The-taps of resistors 36, A6, '55- and [i2 are so adjusted that when the -voltageof-circuit :I is within the desired range of values the potentials of grids 23c, t'fic are slightly .below the critical potential of the thyratrons so that the 'thyratrons remain nonconduotive. This critical potential is negative with respect to cathode .potentialin the type of thyratron above identified. Capacitors .54, .81 are chargedunder a voltage which .isslightly less than the vcltage appe-aring between conductor .35 and the .tap ofiresistor :52.

.Asairesult of the .above described connections, whenthevoltage-of circuit 1 departs iromthe desired range, the potential of one .of the control grids israised and the potential of the other control gridis lowered. When the voltage of circuit i rises, the potential of cathode Ella-impressed on thepositive terminal of resistor 56 .rises to a corresponding extent. The negative potential impressed .irom cathode Mbon the negative termiha}. of resistor 45, however, remains unchanged. The potential of tapdrl and ofgrid'28c thus rises and will eventually reach the critical potential when the voltage of \circuit 1 remains for a suflicientlength of tirneabove a. predetermined value, whiohvalue is determined by the adjustment of the of resistors 35, a and .62. The rise of the potential of grid 28c :is-delayed by capacitors is, El which :draw charging current causin a transient voltage to appear in resistor 45 and temporarily offset the rise in the potential of eathodeiii'ib. The delay in the rise of thepotential of grid .280 to the critical value is relatively large when the increase in the voltage of circuit i is relatively small and the delayis relatively small when the increase in the voltage of circuit i is relatively large.

' When-grid can re'a'chos 'the critical potential, thyratron 28 car-ries cur-rent during every other motor actuates rcgulatorzs to theiproper positionforres'toring-thevoltage of circuit 1 to the desired value. 7 I

Relay 1.9 also disconnects capacitor 5| .irom tap andii-ro'm oneof theterminalsof capacitor 54 and reconnects capacitor 5| with ithe'other terminal zofcapacitorfl through contact 190. A transient positivepotential component is thereby impressed'iontap' ll, the initial value of thislpotential component being the voltage to which capacitor'S'Q was previously charged-from resistor 52. The transientpotential component decays as a result-of the gradual charge of capacitor 5| from resistor :52. The elements of the system connected with capacitor 51' are so chosen that the transientpotential component maintains grid 28c [above critical potential during a period of several cycles evenif the voltage of circuit 34, 35 decreases to an extentsufiicient toreturnthe grid potential below the critical value. Relay !9 is thus ,prevented from operating intermittently in response to a rapid succession of intermittent increasesof the voltage of circuit :7 above the value for which operation. or thyratronZE is'desired.

While thyratron 2B is conducting current the potential of grid 28c never rises above cathode potential. The gridtherefcrecarries an ionic current which-charges capacitors E3 and 49. The-capacitance of capacitor 63 however is so small that the charge of the capacitor is completely dissipated through resistors 48 and 4 5 during the nonconducting half-cycle periods of thyratron 28. Resistor carries a resistance of such high value that the charge of capacitor 49 dueto the ionic current is likewise negligible and is also dissipated during the noneonducting half-cycle periods of thyratron 28.

During operation of regulator 8, capacitor 51 is connected across a portion of resistor 52 through contacts ific, resistor 53 and-conductor 35. The-capacitor is'then gradually charged at a predetermined'portionof the voltage drop in tube M, whereby the capacitor charge is given a relatively largenegative increment the capacitor terminal connected with contact lilo is broughtto a substantial negative potential. Wlien'the voltage of circuit '1 has been returned to substantially the desired value as a result of the operation'of regulator 8, the voltage of circuit is likewise returned to substantially its normal value. The potential of grid 220 is returned belorz' the critical value with a'delay determined by the capacitance of capacitor 49, capacitor 5i then having substantially no delaying action as a result of the connection thereof in series with small capacitor 54. The delay produced by capacitor G9 is small compared to the time required by regulator 8 to move by one step and. serves merely to render thyratron 2S unresponsive to momentary de-- creases in the voltage of circuit l.

When grid 28c has been returned to a potential below the critical potential, thyratron 2B ceases to carry current and relay 19 returns to the deenergized position shown. Contact l9b opens and deenergizes-motor 20, which stops and holds regulator 8 intl'i'e position reached thereby. Contact 19d recloses to reconnect capacitor with tap 41. The voltage to which capacitor 5| was charged from resistor 52 then depresses the potential of grid 28c below the value corresponding to the actual voltage of circuit 1. This depression of the potential of grid 280 is gradually removed while capacitor 5i gradually discharges through resistor 46. Grid 280 thus gradually returns to a potential corresponding to the actual voltage of circuit 1 with a relatively large time delay, whereby regulator 8 is prevented from operating at excessively frequent intervals even if the voltage of circuit I fluctuates rapidly about the desired value.

When the voltage of circuit I decreases below a predetermined value depending on the adjustment of resistors 36, 55 and 62, negative potential impressed from anode 42a on one of the terminals of resistor 55 becomes less while the positive potential impressed from anode 39a on the other terminal of resistor 55 remains unchanged. The potential of tap 56 and of grid 32c therefore rises and, if the voltage of circuit 1 remains below the predetermined value for a sufficient length of time, grid 32c reaches the critical potential of thyratron 32. Current is then supplied to coil 21a through thyratron 32 in the manner above described with respect to coil lea, and motor 20 is caused to drive regulator 8 in the proper direction for raising the voltage of circuit I. The operation of thyratron 32 is then the exact counterpart of the operation of thyratron 28 resulting from a rise in the voltage of circuit 1 and therefore is not described in detail.

The values of the voltage of circuit 1 at which thyratrons 28 and 32 operate may be adjusted by means of taps 47, 56, which may be used as coarse adjustments of the voltages. A fine adjustment of both voltages in the same sense may be obtained by adjusting the tap of resistor 35. The latter adjustment does not change the value of the voltages of circuit 34, 35 at which the thyratrons operate but varies the ratio between the voltage of circuit 34, 35 and the voltage of circuit 1.

The voltages of circuit 1 at which thyratrons 28, 32 operate may be varied in opposite senses by adjusting the tap of resistor 62. The latter adjustment varies the potential of screen grids f 28b, 32b, thereby causing the critical potential of grids 28c, 320 to vary to a corresponding extent. The voltage range within which the voltage of circuit 1 may vary without causing operation of regulator 8 may thus be adjusted while leaving the average value of the voltage unchanged.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a voltage responsive system comprising circuit means for supplying a variable voltage and a current responsive device, the combination of a thyratron having an anode, a cathode and a control grid, said anode being connected to said current responsive device, means for energizing said control grid comprising impedance means connecting said control grid with said circuit means for rendering said thyratronconductive 8-. in responsei to: variation of said voltage through an adjustable predetermined value, means for delaying the response of said thyratron comprising acapacitor connected between said impedance means,- and said cathode, and means comprising an .element of saiddevice, the last said meansbeing responsive to eiierglzation or said current responsivenevice Ior disconnecting said capacitor Irom said impedance means to prevent delay in me response 01 said thyratron and for modifying the charge of said capacitor and ree sponsive to deenergization or said current responsive device 101' reconnecting said capacitor witn said impedance means to restore tile delay in tne response OI said thyratron to said variation or said voltage.

2. in a voltage responsive system comprising circuit means 101' supplying a variable voltage and a current responsive device, tne combination oi a thyratron having an anode, a cathode and a control grid I01 controlling said device, means ior energizing said control grid comprising impedance means connecting said control grid with said circuit means 101' rendering said thyratron conductive in response to variation of said voltage tnrougn an ad ustable predetermined value, means ior delaying the response or said thyratron comprising a capacitor connected between said impedance means and said cathode, and means comprising an element of said device, the last said means being responsive to energization oi said current responsive device for disconnecting said capacitor irom said impedance means to prevent delay in the response of said thyratron and ior giving a negative increment to the charge or said capacitor and responsive to deenergization or said current responsive device i'or reconnecting said capacitor with said impedance means to restore the delay in the response'of said thyratron to said variation of said voltage.

'3. In a voltage responsive system comprising circuit means for supplyin a variable alternatin voltage a current responsive device, the combination of a thyratron having an anode, a cathode and a control grid, for controlling said device, means for energizing said control grid comprisingimpedance means connecting said control grid with said circuit means for rendering said thyratron conductive in response to variation of said voltage through an adjustable predetermined value, and means comprising an element of said device, the last said means being responsive to operation of said current responsive device for impressing a transient positive potential component on said control grid to maintain said control grid at a positive potential for atleast one complete cycle of said variable voltage.

4. In a voltage responsive system comprising circuit means for supplying a variable voltage and a current responsive device, the combination of a thyratron having an anode, a cathode and a control grid, for controlling said device, means for energizing said control grid comprising impedance means connecting said control grid with said circuitmeans for rendering said thyratron conductive in response to variation of said voltage through an adjustable predetermined value, means for delaying the response of said thyratron comprising a capacitor connected between said impedance means and said cathode, a source of negative potential, a resistor and a second capacitor serially connected between said cathode and said impedance means, means comprising an element of said device, the last said means being responsive to energization of said current responsive device for switching the connection of the first said capacitor from the said impedance means tothe juncture point of said second capacitor and said resistor to impress a transient positive potential component on said control grid to prevent delay in the response of said thyratron, and means comprising said element of said device, the last said means being responsive to deenergization of said current responsive device for reconnectin the first said capacitor with said impedance means to restore the delay in the response of said thyratron to said variation of said voltage.

5. In a voltage responsive system comprising circuit means for supplying a variable voltage and first and second current responsive devices, the combination of a first thyratron for controlling said first current responsive device, a first adjustable connection between the control grid of said first thyratron and said circuit means for rendering said first thyratron conductive in response to variation of said voltage above a first predetermined adjustable value, first impedance means connected with said first thyratron for delaying the response of said first thyratron to said vo1tage variations above said first predetermined adjustable value, first switch means connected with said first impedance means responsive to operation of said first current responsive device for rendering inoperative said first impedance means, a second thyratron for controlling said second current responsive device, a second adjustable connection between the control grid of said second thyratron and said circuit means for rendering said second thyratron conductive in response to variation of said voltage below a second predetermined adjustable value, second impedance means connected with said second thyratron for delayin the response of said second thyratron to said voltage variations below said second predetermined adjustable value, second switch means connected with said second impedance means responsive to operation of said second current responsive device for rendering inoperative said second impedance means, and common adjustable means in said adjustable con- 10 nections for simultaneously adjusting said first and second voltage values.

6. In a voltage responsive system comprising circuit means for supplying a variable voltage and first and second current responsive devices, the combination of a first thyratron for controlling said first current responsive device, a first adjustable connection between the control grid of said first thyratron and said circuit means for rendering said first thyratron conductive in response to variation of said voltage above a first predetermined adjustable value, first means for delaying the response of said first thyratron to said voltage variations above said first predetermined adjustable value, first means responsive to operation of said first current responsive device for rendering inoperative said first response delaying means, a second thyratron for controlling said second current responsive device, a second adjustable connection between the control grid of said second thyratron and said circuit means for rendering said second thyratron conductive in response to variation of said voltage below a second predetermined adjustable value, second means for delaying the response of said second thyratron to said voltage variations below said second predetermined adjustable value, means responsive to operation of said second current responsive device for rendering inoperative said second response delaying means, and common adjustable means in said adjustable connections operable for simultaneously varying said first and second voltage values in the same sense.

RUDOLPH M. SE'ROTA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Certificate of Correction Patent No. 2,516,348 July 25, 1950 RUDOLPH M. SEROTA It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 44, after the Word voltage insert and; lines 46 and 64, after grid strike out the comma;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 24th day of October, A. D. 1950.

THOMAS F. MURPHY,

Assistant Gammz'ssz'oner of Patents.

Certificate of Correction Patent No. 2,516,348 July 25, 1950 RUDOLPH M. SEROTA It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 8, line 44, after the Word voltage insert and; lines 46 and 64, after grid strike out the comma;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 24th day of October, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

